Not single but periodic injections of synovial mesenchymal stem cells maintain viable cells in knees and inhibit osteoarthritis progression in rats

Scanning electron microscopy analysis of synovial and adipose mesenchymal stem cells adhering to cartilage

Introduction

Mesenchymal stem cells (MSCs) are increasingly used for intra-articular injections in the treatment of knee osteoarthritis. The aim of this study was to use scanning electron microscopy (SEM) to compare the morphological characteristics of synovial and adipose MSCs.

Methods

Synovium and adipose tissues were concurrently harvested from eight patients with knee osteoarthritis. Suspensions of both synovial and adipose MSCs were examined to identify the presence of microspikes. In addition to this study, the MSC suspensions in four patients were applied to abraded porcine cartilage discs and observed 10 s, 10 min, and 1 h later.

Results

The median percentage of cells exhibiting microspikes was 14% for synovial MSC suspensions and 13% for adipose MSC suspensions; this difference was not statistically significant (n = 8). No notable differences were detected in the number of adherent cells or in the proportion of cells displaying microspikes or pseudopodia. Strong correlations were found between the proportion of cells with pseudopodia and the number of attached cells for both synovial (r = 0.92, n = 12) and adipose (r = 0.86, n = 12) MSCs, with no significant difference in the correlation coefficients between the two groups.

Conclusion

SEM analysis revealed no obvious differences in morphological characteristics during MSC adhesion to cartilage for either synovial or adipose MSCs.

Therapeutic Effects of Mesenchymal Stem Cells Derived from Bone Marrow and Adipose Tissue in a Rat Model of Temporomandibular Osteoarthritis

OBJECTIVES

To examine the potential of intra-articular administration of mesenchymal stem cells (MSCs) derived from bone marrow or adipose tissue to mitigate synovial inflammation in a rat model of temporomandibular joint (TMJ) osteoarthritis (OA).

METHODS

In this experimental study, 40 rats were divided into 4 groups: (1) Control group; (2) Untreated TMJ-OA group; (3) TMJ-OA group treated with bone marrow-derived MSCs; (4) TMJ-OA group treated with adipose tissue-derived MSCs. The TMJ-OA model was established by inducing synovial inflammation through the intra-articular administration of complete Freund's adjuvant (CFA). After 8 weeks of TMJ-OA establishment, the animals were sacrificed and each mandibular condyle was extracted for histological evaluation.

RESULTS

The untreated TMJ-OA group had significantly higher synovial inflammation, as indicated microscopically by higher grades of synovial membrane hyperplasia and adhesion, vascular vasodilation, and fibrin deposition than the control group (p < 0.001). Both TMJ-OA groups treated with MSCs had lower grades of synovial inflammation and less severe synovitis than the untreated TMJ-OA group (p < 0.001). The TMJ-OA group treated with adipose tissue-derived MSCs showed lower grades of synovial membrane hyperplasia and higher grades of fibrin deposition than the that treated with bone marrow-derived MSCs (p < 0.001). Other indicators of synovial inflammation and synovitis severity were comparable between the two treatment groups.

CONCLUSIONS

Administration of CFA to the TMJ-OA rat model augmented synovial inflammation. Intra-articular administration of MSCs derived from either bone marrow or adipose tissue attenuated the microscopic manifestations of this inflammation, indicating the therapeutic potential of this treatment for TMJ-OA.

Synovial mesenchymal stem cells secrete more lubricin than adipose mesenchymal stem cells after injection into rat osteoarthritis knees

Intra-articular injection of mesenchymal stem cells (MSCs) is envisioned as a solution for knee osteoarthritis (OA). Although synovial MSCs (SyMSCs) are promising for cartilage regeneration, the clinical choice is usually adipose MSCs (AdMSCs). However, the similarities/differences in the mode of action between SyMSCs and AdMSCs remain unclear. Here, we compared factors secreted by human SyMSCs and AdMSCs after injection into OA knees. Human SyMSCs or AdMSCs were injected into the knees of rat partial meniscectomy models. The next day, the knee joints were collected to analyze the distribution of injected MSCs and transcriptome changes in the human MSCs and rat synovium. Non-injected MSCs were mixed with rat synovium as a control. After injection, no difference was apparent in intra-articular distribution of the SyMSCs or AdMSCs. RNA sequencing demonstrated an enrichment of cytokine-cytokine receptor interaction-related genes in both human SyMSCs and AdMSCs after injection. Differentially expressed genes (DEGs) specific to SyMSCs were associated with cartilage matrix synthesis and homeostasis. PCR analysis of the matrisome-related DEGs showed significantly higher expression of PRG4 in SyMSCs than in AdMSCs after injection. Immunostaining also confirmed a significantly greater expression of lubricin by SyMSCs than by AdMSCs. These findings indicate that SyMSCs will be a more promising treatment for OA.

Therapeutic potential of dedifferentiated fat cells in a rat model of osteoarthritis of the knee

Introduction

Mature adipocyte-derived dedifferentiated fat cells (DFATs) represent a subtype of multipotent cells that exhibit comparable phenotypic and functional characteristics to adipose-derived stem cells (ASCs). In this study, we assessed the chondroprotective properties of intra-articularly administrated DFATs in a rat model of osteoarthritis (OA). We also investigated in vitro the expression of anti-inflammatory and chondroprotective genes in DFATs prepared from the infrapatellar fat pad (IFP) and subcutaneous adipose-tissue (SC) of human origin.

Methods

In the cell transplantation experiment, rats were assigned to the DFAT and Control group (n = 10 in each group) and underwent anterior cruciate ligament transection (ACLT) accompanied by medial meniscus resection (MMx) to induce OA. One week later, they received intra-articular injections of 1 × 106 DFATs (DFAT group) or PBS (control group) four times, with a weekly administration frequency. Macroscopic and microscopic evaluations were conducted five weeks post-surgery. In the in vitro experiments. DFATs derived from the IFP (IFP-DFATs) and SC (SC-DFATs) were prepared from donor-matched tissue samples (n = 3). The gene expression of PTGS2, TNFAIP6, PRG4, BMP2, and BMP6 under TNF-α or IFN-γ stimulation in these cells was evaluated using RT-PCR. Furthermore, the effect of co-culturing synovial fibroblasts with DFATs on the gene expression of ADAMTS4 and IL-6 were evaluated.

Results

Intra-articular injections of DFATs significantly inhibited cartilage degeneration in the rat OA model induced by ACLT and MMx. RT-PCR analysis revealed that both IFP-DFATs and SC-DFATs upregulated the expression of genes involved in immune regulation, anti-inflammation, and cartilage protection such as PTGS2, TNFAIP6, and BMP2, under stimulation by inflammatory cytokines. Co-culture with DFATs suppressed the expression of ADAMTS4 and IL6 in synovial fibroblasts.

Conclusions

The intra-articular injection of DFATs resulted in chondroprotective effects in the rat OA model. Both SC-DFATs and IFP-DFATs induced the expression of anti-inflammatory and chondroprotective genes in vitro. These results indicate that DFATs appear to possess therapeutic potential in inhibiting cartilage degradation and could serve as a promising cellular resource for OA treatment.

Extracellular vesicles derived from mesenchymal stem cells mediate extracellular matrix remodeling in osteoarthritis through the transport of microRNA-29a

BACKGROUND

Knee osteoarthritis (KOA) is a common orthopedic condition with an uncertain etiology, possibly involving genetics and biomechanics. Factors like changes in chondrocyte microenvironment, oxidative stress, inflammation, and immune responses affect KOA development. Early-stage treatment options primarily target symptom relief. Mesenchymal stem cells (MSCs) show promise for treatment, despite challenges. Recent research highlights microRNAs (miRNAs) within MSC-released extracellular vesicles that can potentially promote cartilage regeneration and hinder KOA progression. This suggests exosomes (Exos) as a promising avenue for future treatment. While these findings emphasize the need for effective KOA progression management, further safety and efficacy validation for Exos is essential.

AIM

To explore miR-29a's role in KOA, we'll create miR-29a-loaded vesicles, testing for early treatment in rat models.

METHODS

Extraction of bone marrow MSC-derived extracellular vesicles, preparation of engineered vesicles loaded with miR-29a using ultrasonication, and identification using quantitative reverse transcription polymerase chain reaction; after establishing a rat model of KOA, rats were randomly divided into three groups: Blank control group injected with saline, normal extracellular vesicle group injected with normal extracellular vesicle suspension, and engineered extracellular vesicle group injected with engineered extracellular vesicle suspension. The three groups were subjected to general behavioral observation analysis, imaging evaluation, gross histological observation evaluation, histological detection, and immunohistochemical detection to compare and evaluate the progress of various forms of arthritis.

RESULTS

General behavioral observation results showed that the extracellular vesicle group and engineered extracellular vesicle group had better performance in all four indicators of pain, gait, joint mobility, and swelling compared to the blank control group. Additionally, the engineered extracellular vesicle group had better pain relief at 4 wk and better knee joint mobility at 8 wk compared to the normal extracellular vesicle group. Imaging examination results showed that the blank control group had the fastest progression of arthritis, the normal extracellular vesicle group had a relatively slower progression, and the engineered extracellular vesicle group had the slowest progression. Gross histological observation results showed that the blank control group had the most obvious signs of arthritis, the normal extracellular vesicle group showed signs of arthritis, and the engineered extracellular vesicle group showed no significant signs of arthritis. Using the Pelletier gross score evaluation, the engineered extracellular vesicle group had the slowest progression of arthritis. Results from two types of staining showed that the articular cartilage of rats in the normal extracellular vesicle and engineered extracellular vesicle groups was significantly better than that of the blank control group, and the engineered extracellular vesicle group had the best cartilage cell and joint surface condition. Immunohistochemical detection of type II collagen and proteoglycan showed that the extracellular matrix of cartilage cells in the normal extracellular vesicle and engineered extracellular vesicle groups was better than that of the blank control group. Compared to the normal extracellular vesicle group, the engineered extracellular vesicle group had a better regulatory effect on the extracellular matrix of cartilage cells.

CONCLUSION

Engineered Exos loaded with miR-29a can exert anti-inflammatory effects and maintain extracellular matrix stability, thereby protecting articular cartilage, and slowing the progression of KOA.

Beneficial Effect of Sirolimus-Pretreated Mesenchymal Stem Cell Implantation on Diabetic Retinopathy in Rats

BACKGROUND

Diabetic retinopathy (DR) is a vision-threatening complication that affects virtually all diabetic patients. Various treatments have been attempted, but they have many side effects and limitations. Alternatively, stem cell therapy is being actively researched, but it faces challenges due to a low cell survival rate. In this study, stem cells were pretreated with sirolimus, which is known to promote cell differentiation and enhance the survival rate. Additionally, the subconjunctival route was employed to reduce complications following intravitreal injections.

METHODS

Diabetes mellitus was induced by intraperitoneal injection of 55 mg/kg of streptozotocin (STZ), and DR was confirmed at 10 weeks after DM induction through electroretinogram (ERG). The rats were divided into four groups: intact control group (INT), diabetic retinopathy group (DR), DR group with subconjunctival MSC injection (DR-MSC), and DR group with subconjunctival sirolimus-pretreated MSC injection (DR-MSC-S). The effects of transplantation were evaluated using ERG and histological examinations.

RESULTS

The ERG results showed that the DR-MSC-S group did not significantly differ from the INT in b-wave amplitude and exhibited significantly higher values than the DR-MSC and DR groups (p < 0.01). The flicker amplitude results showed that the DR-MSC and DR-MSC-S groups had significantly higher values than the DR group (p < 0.01). Histological examination revealed that the retinal layers were thinner in the DR-induced groups compared to the INT group, with the DR-MSC-S group showing the thickest retinal layers among them.

CONCLUSIONS

Subconjunctival injection of sirolimus-pretreated MSCs can enhance retinal function and mitigate histological changes in the STZ-induced DR rat model.

Protecting the regenerative environment: selecting the optimal delivery vehicle for cartilage repair-a narrative review

Focal cartilage defects are common in youth and older adults, cause significant morbidity and constitute a major risk factor for developing osteoarthritis (OA). OA is the most common musculoskeletal (MSK) disease worldwide, resulting in pain, stiffness, loss of function, and is currently irreversible. Research into the optimal regenerative approach and methods in the setting of either focal cartilage defects and/or OA holds to the ideal of resolving both diseases. The two fundamentals required for cartilage regenerative treatment are 1) the biological element contributing to the regeneration (e.g., direct application of stem cells, or of an exogenous secretome), and 2) the vehicle by which the biological element is suspended and delivered. The vehicle provides support to the regenerative process by providing a protective environment, a structure that allows cell adherence and migration, and a source of growth and regenerative factors that can activate and sustain regeneration. Models of cartilage diseases include osteochondral defect (OCD) (which usually involve one focal lesion), or OA (which involves a more diffuse articular cartilage loss). Given the differing nature of these models, the optimal regenerative strategy to treat different cartilage diseases may not be universal. This could potentially impact the translatability of a successful approach in one condition to that of the other. An analogy would be the repair of a pothole (OCD) versus repaving the entire road (OA). In this narrative review, we explore the existing literature evaluating cartilage regeneration approaches for OCD and OA in animal then in human studies and the vehicles used for each of these two conditions. We then highlight strengths and challenges faced by the different approaches presented and discuss what might constitute the optimal cartilage regenerative delivery vehicle for clinical cartilage regeneration.

Special Issue "Mesenchymal Stromal Cells' Involvement in Human Diseases and Their Treatment"

Mesenchymal stromal cells (MSCs) are multipotent, non-hematopoietic cells that have the ability to differentiate into several mature cell types, including adipocytes, chondrocytes, osteoblasts, and myoblasts [...].

The autologous chondral platelet-rich plasma matrix implantation. A new therapy in cartilage repair and regeneration: macroscopic and biomechanical study in an experimental sheep model

Introduction

Articular cartilage injuries are a severe problem, and the treatments for these injuries are complex. The present study investigates a treatment for full-thickness cartilage defects called Autologous Chondral Platelet Rich Plasma Matrix Implantation (PACI) in a sheep model.

Methods

Chondral defects 8 mm in diameter were surgically induced in the medial femoral condyles of both stifles in eight healthy sheep. Right stifles were treated with PACI and an intraarticular injection with a plasma rich in growth factors (PRGF) solution [treatment group (TRT)], while an intraarticular injection of Ringer's lactate solution was administered in left stifles [Control group (CT)]. The limbs' function was objectively assessed with a force platform to obtain the symmetry index, comparing both groups. After 9 and 18 months, the lesions were macroscopically evaluated using the International Cartilage Repair Society and Goebel scales.

Results

Regarding the symmetry index, the TRT group obtained results similar to those of healthy limbs at 9 and 18 months after treatment. Regarding the macroscopic assessment, the values obtained by the TRT group were very close to those of normal cartilage and superior to those obtained by the CT group at 9 months.

Conclusion

This new bioregenerative treatment modality can regenerate hyaline articular cartilage. High functional outcomes have been reported, together with a good quality repair tissue in sheep. Therefore, PACI treatment might be a good therapeutic option for full-thickness chondral lesions.

Controlled-Release Hydrogel Microspheres to Deliver Multipotent Stem Cells for Treatment of Knee Osteoarthritis

Osteoarthritis (OA) is the most common form of joint disease affecting articular cartilage and peri-articular tissues. Traditional treatments are insufficient, as they are aimed at mitigating symptoms. Multipotent Stromal Cell (MSC) therapy has been proposed as a treatment capable of both preventing cartilage destruction and treating symptoms. While many studies have investigated MSCs for treating OA, therapeutic success is often inconsistent due to low MSC viability and retention in the joint. To address this, biomaterial-assisted delivery is of interest, particularly hydrogel microspheres, which can be easily injected into the joint. Microspheres composed of hyaluronic acid (HA) were created as MSC delivery vehicles. Microrheology measurements indicated that the microspheres had structural integrity alongside sufficient permeability. Additionally, encapsulated MSC viability was found to be above 70% over one week in culture. Gene expression analysis of MSC-identifying markers showed no change in CD29 levels, increased expression of CD44, and decreased expression of CD90 after one week of encapsulation. Analysis of chondrogenic markers showed increased expressions of aggrecan (ACAN) and SRY-box transcription factor 9 (SOX9), and decreased expression of osteogenic markers, runt-related transcription factor 2 (RUNX2), and alkaline phosphatase (ALPL). In vivo analysis revealed that HA microspheres remained in the joint for up to 6 weeks. Rats that had undergone destabilization of the medial meniscus and had overt OA were treated with empty HA microspheres, MSC-laden microspheres, MSCs alone, or a control vehicle. Pain measurements taken before and after the treatment illustrated temporarily decreased pain in groups treated with encapsulated cells. Finally, the histopathological scoring of each group illustrated significantly less OA damage in those treated with encapsulated cells compared to controls. Overall, these studies demonstrate the potential of using HA-based hydrogel microspheres to enhance the therapeutic efficacy of MSCs in treating OA.

Comparative Effects of Intra-Articular versus Intravenous Mesenchymal Stromal Cells Therapy in a Rat Model of Osteoarthritis by Destabilization of Medial Meniscus

Transplanted mesenchymal stromal cells (MSCs) exhibit a robust anti-inflammatory and homing capacity in response to high inflammatory signals, as observed in studies focused on rheumatic diseases that target articular cartilage (AC) health. However, AC degradation in osteoarthritis (OA) does not necessarily coincide with a highly inflammatory joint profile. Often, by the time patients seek medical attention, they already have damaged AC. In this study, we examined the therapeutic potential of a single bone marrow MSC transplant (2 × 106 cells/kgbw) through two different routes: intra-articular (MSCs-IAt) and intravenous (MSCs-IVt) in a preclinical model of low-grade inflammatory OA with an established AC degeneration. OA was induced through the destabilization of the medial meniscus (DMM) in female Wistar Kyoto rats. The animals received MSCs 9 weeks after surgery and were euthanized 4 and 12 weeks post-transplant. In vivo and ex vivo tracking of MSCs were analyzed via bioluminescence and imaging flow cytometry, respectively. Cytokine/chemokine modulation in serum and synovial fluid was measured using a multiplex panel. AC degeneration was quantified through histology, and hindlimb muscle balance was assessed with precision weighing. To our knowledge, we are the first group to show the in vivo (8 h) and ex vivo (12 h) homing of cells to the DMM-OA joint following MSCs-IVt. In the case of MSCs-IAt, the detection of cellular bioluminescence at the knee joint persisted for up to 1 week. Intriguingly, intra-articular saline injection (placebo-IAt) resulted in a worse prognosis of OA when compared to a non-invasive control (placebo-IVt) without joint injection. The systemic cytokines/chemokines profile exhibited a time-dependent variation between transplant routes, displaying a transient anti-inflammatory systemic response for both MSCs-IVt and MSCs-IAt. A single injection of MSCs, whether administered via the intra-articular or intravenous route, performed 9 weeks after DMM surgery, did not effectively inhibit AC degeneration when compared to a non-invasive control.

Using Pre-Clinical Studies to Explore the Potential Clinical Uses of Exosomes Secreted from Induced Pluripotent Stem Cell-Derived Mesenchymal Stem cells

Recent studies of exosomes derived from mesenchymal stem cells (MSCs) have indicated high potential clinical applications in many diseases. However, the limited source of MSCs impedes their clinical research and application. Most recently, induced pluripotent stem cells (iPSCs) have become a promising source of MSCs. Exosome therapy based on iPSC-derived MSCs (iMSCs) is a novel technique with much of its therapeutic potential untapped. Compared to MSCs, iMSCs have proved superior in cell proliferation, immunomodulation, generation of exosomes capable of controlling the microenvironment, and bioactive paracrine factor secretion, while also theoretically eliminating the dependence on immunosuppression drugs. The therapeutic effects of iMSC-derived exosomes are explored in many diseases and are best studied in wound healing, cardiovascular disease, and musculoskeletal pathology. It is pertinent clinicians have a strong understanding of stem cell therapy and the latest advances that will eventually translate into clinical practice. In this review, we discuss the various applications of exosomes derived from iMSCs in clinical medicine.

Scalable mesenchymal stem cell enrichment from bone marrow aspirate using deterministic lateral displacement (DLD) microfluidic sorting

The growing interest in regenerative medicine has opened new avenues for novel cell therapies using stem cells. Bone marrow aspirate (BMA) is an important source of stromal mesenchymal stem cells (MSCs). Conventional MSC harvesting from BMA relies on archaic centrifugation methods, often leading to poor yield due to osmotic stress, high centrifugation force, convoluted workflow, and long experimental time (∼2-3 hours). To address these issues, we have developed a scalable microfluidic technology based on deterministic lateral displacement (DLD) for MSC isolation. This passive, label-free cell sorting method capitalizes on the morphological differences between MSCs and blood cells (platelets and RBCs) for effective separation using an inverted L-shaped pillar array. To improve throughput, we developed a novel multi-chip DLD system that can process 2.5 mL of raw BMA in 20 ± 5 minutes, achieving a 2-fold increase in MSC recovery compared to centrifugation methods. Taken together, we envision that the developed DLD platform will enable fast and efficient isolation of MSCs from BMA for effective downstream cell therapy in clinical settings.

Harnessing knee joint resident mesenchymal stem cells in cartilage tissue engineering

Osteoarthritis (OA) is a widespread clinical disease characterized by cartilage degeneration in middle-aged and elderly people. Currently, there is no effective treatment for OA apart from total joint replacement in advanced stages. Mesenchymal stem cells (MSCs) are a type of adult stem cell with diverse differentiation capabilities and immunomodulatory potentials. MSCs are known to effectively regulate the cartilage microenvironment, promote cartilage regeneration, and alleviate OA symptoms. As a result, they are promising sources of cells for OA therapy. Recent studies have revealed the presence of resident MSCs in synovial fluid, synovial membrane, and articular cartilage, which can be collected as knee joint-derived MSCs (KJD-MSC). Several preclinical and clinical studies have demonstrated that KJD-MSCs have great potential for OA treatment, whether applied alone, in combination with biomaterials, or as exocrine MSCs. In this article, we will review the characteristics of MSCs in the joints, including their cytological characteristics, such as proliferation, cartilage differentiation, and immunomodulatory abilities, as well as the biological function of MSC exosomes. We will also discuss the use of tissue engineering in OA treatment and introduce the concept of a new generation of stem cell-based tissue engineering therapy, including the use of engineering, gene therapy, and gene editing techniques to create KJD-MSCs or KJD-MSC derivative exosomes with improved functionality and targeted delivery. These advances aim to maximize the efficiency of cartilage tissue engineering and provide new strategies to overcome the bottleneck of OA therapy. STATEMENT OF SIGNIFICANCE: This research will provide new insights into the medicinal benefit of Joint resident Mesenchymal Stem Cells (MSCs), specifically on its cartilage tissue engineering ability. Through this review, the community will further realize promoting joint resident mesenchymal stem cells, especially cartilage progenitor/MSC-like progenitor cells (CPSC), as a preventive measure against osteoarthritis and cartilage injury. People and medical institutions may also consider cartilage derived MSC as an alternative approach against cartilage degeneration. Moreover, the discussion presented in this study will convey valuable information for future research that will explore the medicinal benefits of cartilage derived MSC.

Inorganic nanoparticle-integrated mesenchymal stem cells: A potential biological agent for multifaceted applications

Mesenchymal stem cell (MSC)-based therapies are flourishing. MSCs could be used as potential therapeutic agents for regenerative medicine due to their own repair function. Meanwhile, the natural predisposition toward inflammation or injury sites makes them promising carriers for targeted drug delivery. Inorganic nanoparticles (INPs) are greatly favored for their unique properties and potential applications in biomedical fields. Current research has integrated INPs with MSCs to enhance their regenerative or antitumor functions. This model also allows the in vivo fate tracking of MSCs in multiple imaging modalities, as many INPs are also excellent contrast agents. Thus, INP-integrated MSCs would be a multifunctional biologic agent with great potential. In this review, the current roles performed by the integration of INPs with MSCs, including (i) enhancing their repair and regeneration capacity via the improvement of migration, survival, paracrine, or differentiation properties, (ii) empowering tumor-killing ability through agent loaded or hyperthermia, and (iii) conferring traceability are summarized. An introduction of INP-integrated MSCs for simultaneous treatment and tracking is also included. The promising applications of INP-integrated MSCs in future treatments are emphasized and the challenges to their clinical translation are discussed.

Formyl peptide receptors in bone research

PURPOSE/AIM OF THE STUDY

The formyl peptide receptor (FPR) participates in the immune response, with roles in infection and inflammation. In this review article, we summarize the current literature on these roles before discussing the function of FPRs in the pathogenesis of musculoskeletal disorders including osteoarthritis (OA), degenerative disc disease (DDD), and rheumatoid arthritis (RA). Additionally, we discuss the potential diagnostic and therapeutic roles of FPRs in these domains.

METHODS

PubMed and Ovid MEDLINE searches were performed from 1965 through March 2022. Keywords included "FPR, tissue expression, inflammation, infection, musculoskeletal disorder, bone, rheumatoid arthritis, osteoarthritis, degenerative disc disease, mitochondria."

RESULTS

Sixty-nine studies were included in this review article. FPRs appear to be ubiquitous in the pathogenesis, diagnosis, and treatment of common musculoskeletal disorders. They can potentially be utilized for the earlier diagnosis of OA and DDD. They may be employed with mesenchymal stem cells (MSCs) to reverse OA and DDD pathologies. With anti-inflammatory, anti-osteolytic, and pro-angiogenic functions, they may broaden treatment options in RA.

CONCLUSIONS

FPRs appear to be heavily involved in the pathogenesis of common musculoskeletal conditions, including arthritis, degenerative disc disease, and rheumatoid arthritis. Furthermore, they demonstrate much promise in the diagnosis and treatment of these conditions. Their roles should continue to be explored.

Intravenous injection of adipose-derived mesenchymal stromal cells benefits gait and inflammation in a spontaneous osteoarthritis model

Osteoarthritis (OA) is a leading cause of morbidity among aging populations, yet symptom and/or disease-modification remains elusive. Adipose-derived mesenchymal stromal cells (adMSCs) have demonstrated immunomodulatory and anti-inflammatory properties that may alleviate clinical signs and interrupt disease onset and progression. Indeed, multiple manuscripts have evaluated intra-articular administration of adMSCs as a therapeutic; however, comparatively few evaluations of systemic delivery methods have been published. Therefore, the aim of this study was to evaluate the short-term impact of intravenous (IV) delivery of allogeneic adMSCs in an established model of spontaneous OA, the Hartley guinea pig. Animals with moderate OA received once weekly injections of 2 × 106 adMSCs or vehicle control for 4 weeks in peripheral veins; harvest occurred 2 weeks after the final injection. Systemic administration of adMSCs resulted in no adverse effects and was efficacious in reducing clinical signs of OA (as assessed by computer-aided gait analysis) compared to control injected animals. Further, there were significant decreases in key inflammatory mediators (including monocyte chemoattractant protein-1, tumor necrosis factor, and prostaglandin E2 ) both systemically (liver, kidney, and serum) and locally in the knee (joint tissues and synovial fluid) in animals treated with IV adMSCs relative to controls (as per enzyme-linked immunosorbent assay and/or immunohistochemistry, dictated by tissue sample). Thus, systemic administration of adMSCs by IV injection significantly improved gait parameters and reduced both systemic and intra-articular inflammatory mediators in animals with OA. These findings demonstrate the potential utility of alternative delivery approaches for cellular therapy of OA, particularly for patients with multiple affected joints.

Micromolding-based encapsulation of mesenchymal stromal cells in alginate for intraarticular injection in osteoarthritis

Osteoarthritis (OA) is an inflammatory joint disease that affects cartilage, subchondral bone, and joint tissues. Undifferentiated Mesenchymal Stromal Cells are a promising therapeutic option for OA due to their ability to release anti-inflammatory, immuno-modulatory, and pro-regenerative factors. They can be embedded in hydrogels to prevent their tissue engraftment and subsequent differentiation. In this study, human adipose stromal cells are successfully encapsulated in alginate microgels via a micromolding method. Microencapsulated cells retain their in vitro metabolic activity and bioactivity and can sense and respond to inflammatory stimuli, including synovial fluids from OA patients. After intra-articular injection in a rabbit model of post-traumatic OA, a single dose of microencapsulated human cells exhibit properties matching those of non-encapsulated cells. At 6 and 12 weeks post-injection, we evidenced a tendency toward a decreased OA severity, an increased expression of aggrecan, and a reduced expression of aggrecanase-generated catabolic neoepitope. Thus, these findings establish the feasibility, safety, and efficacy of injecting cells encapsulated in microgels, opening the door to a long-term follow-up in canine OA patients.

Mesenchymal stem cells in osteoarthritis: The need for translation into clinical therapy

Widely used for cell-based therapy in various medical fields, mesenchymal stem cells (MSCs) show capacity for anti-inflammatory effects, anti-apoptotic activity, immunomodulation, and tissue repair and regeneration. As such, they can potentially be used to treat osteoarthritis (OA). However, MSCs from different sources have distinct advantages and disadvantages, and various animal models and clinical trials using different sources of MSCs are being conducted in OA regenerative medicine. It is now widely believed that the primary tissue regeneration impact of MSCs is via paracrine effects, rather than direct differentiation and replacement. Cytokines and molecules produced by MSCs, including extracellular vesicles with mRNAs, microRNAs, and bioactive substances, play a significant role in OA repair. This chapter outlines the properties of MSCs and recent animal models and clinical trials involving MSCs-based OA therapy, as well as how the paracrine effect of MSCs acts in OA cartilage repair. Additionally, it discusses challenges and controversies in MSCs-based OA therapy. Despite its limits and unanticipated hazards, MSCs have the potential to be translated into therapeutic therapy for future OA treatment.

Autologous Synovial Mesenchymal Stem Cell Transplantation Suppresses Inflammation Caused by Synovial Harvesting and Promotes Healing in a Micro Minipig Repaired Meniscus Model

PURPOSE

Allogeneic synovial mesenchymal stem cells (MSCs) effectively promote meniscus healing in micro minipigs. We investigated the effect of autologous synovial MSC transplantation on meniscus healing in a micro minipig model of meniscus repair showing synovitis after synovial harvesting.

MATERIALS AND METHODS

Synovium was harvested from the left knee of the micro minipigs after arthrotomy and used to prepare synovial MSCs. The left medial meniscus in the avascular region was injured, repaired, and transplanted with synovial MSCs. First, synovitis was compared after 6 weeks in knees with and without synovial harvesting. Second, the repaired meniscus was compared for the autologous MSC group and the control group (in which synovium was harvested but MSCs were not transplanted) 4 weeks after transplantation.

RESULTS

Synovitis was more severe in knees subjected to synovium harvesting than in knees not subjected to harvesting. Menisci treated with autologous MSCs showed no red granulation at the tear of the meniscus, but menisci not treated with MSCS showed red granulation. Macroscopic scores, inflammatory cell infiltration scores, and matrix scores assessed by toluidine blue staining were all significantly better in the autologous MSC group than in the control group without MSCs (n = 6).

CONCLUSION

Autologous synovial MSC transplantation suppressed the inflammation caused by synovial harvesting in micro minipigs and promoted healing of the repaired meniscus.

Advances in Mesenchymal Stem Cell Therapy for Osteoarthritis: From Preclinical and Clinical Perspectives

The prevalence of osteoarthritis (OA), a degenerative disorder of joints, has substantially increased in recent years. Its key pathogenic hallmarks include articular cartilage destruction, synovium inflammation, and bone remodeling. However, treatment outcomes are unsatisfactory. Until recently, common therapy methods, such as analgesic and anti-inflammatory treatments, were aimed to treat symptoms that cannot be radically cured. Mesenchymal stem cells (MSCs), i.e., mesoderm non-hematopoietic cells separated from bone marrow, adipose tissue, umbilical cord blood, etc., have been intensively explored as an emerging technique for the treatment of OA over the last few decades. According to existing research, MSCs may limit cartilage degradation in OA by interfering with cellular immunity and secreting a number of active chemicals. This study aimed to examine the potential mechanism of MSCs in the treatment of OA and conduct a thorough review of both preclinical and clinical data.

Gene Delivery to Chondrocytes

Delivering genes to chondrocytes offers new possibilities both clinically, for treating conditions that affect cartilage, and in the laboratory, for studying the biology of chondrocytes. Advances in gene therapy have created a number of different viral and non-viral vectors for this purpose. These vectors may be deployed in an ex vivo fashion, where chondrocytes are genetically modified outside the body, or by in vivo delivery where the vector is introduced directly into the body; in the case of articular and meniscal cartilage in vivo delivery is typically by intra-articular injection. Ex vivo delivery is favored in strategies for enhancing cartilage repair as these can be piggy-backed on existing cell-based technologies, such as autologous chondrocyte implantation, or used in conjunction with marrow-stimulating techniques such as microfracture. In vivo delivery to articular chondrocytes has proved more difficult, because the dense, anionic, extra-cellular matrix of cartilage limits access to the chondrocytes embedded within it. As Grodzinsky and colleagues have shown, the matrix imposes strict limits on the size and charge of particles able to diffuse through the entire depth of articular cartilage. Empirical observations suggest that the larger viral vectors, such as adenovirus (~100 nm), are unable to transduce chondrocytes in situ following intra-articular injection. However, adeno-associated virus (AAV; ~25 nm) is able to do so in horse joints. AAV is presently in clinical trials for arthritis gene therapy, and it will be interesting to see whether human chondrocytes are also transduced throughout the depth of cartilage by AAV following a single intra-articular injection. Viral vectors have been used to deliver genes to the intervertebral disk but there has been little research on gene transfer to chondrocytes in other cartilaginous tissues such as nasal, auricular or tracheal cartilage.

Safety of using cultured cells with trisomy 7 in cell therapy for treating osteoarthritis

Cell therapy is a promising alternative treatment approach currently under study for osteoarthritis (OA), the most common chronic musculoskeletal disease. However, the mesenchymal stem cells (MSCs) used in cell therapy to treat OA are usually expanded in vitro to obtain sufficient numbers for transplantation, and their safety has not been fully assessed from multiple perspectives. Analysis of karyotypic abnormalities, in particular, is important to ensure the safety of cells; however, chromosomal mutations may also occur during the cell-expansion process. In addition, there have been many reports showing chromosome abnormalities, mainly trisomy 7, in the cartilage and synovium of patients with OA as well as in normal tissues. The suitability of cells with these karyotypic abnormalities as cells for cell therapy has not been evaluated. Recently, we assessed the safety of using cells with trisomy 7 from the osteoarthritic joint of a patient for transplantation, and we followed up with the patient for 5 years. This study showed analysis for copy number variant and whole-genome sequencing, compared with blood DNA from the same patient. We did not find any abnormalities in the genes regardless of trisomy 7. No side effects were observed for at least 5 years in the human clinical study. This suggests that the transplantation of cultured cells with trisomy 7 isolated from an osteoarthritic joint and transplanted into the osteoarthritic joints of the same person is not expected to cause serious adverse events. However, it is unclear what problems may arise in the case of allogeneic transplantation. Different types of risks will also exist depending on other transplantation routes, such as localization to the knee-joint only or circulation inflow and lung entrapment. In addition, since the cause of trisomy 7 occurrence remains unclear, it is necessary to clarify the mechanism of trisomy 7 in OA to perform cell therapy for OA patients in a safe manner.

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Trisomy 7 is frequently observed in the cartilage and synovium of patients with OA.

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MSCs with trisomy 7 did not form tumor after transplantation into mice.

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No side effects were observed 5 years after transplantation of MSCs with trisomy 7.

Cellular therapy and tissue engineering for cartilage repair

Articular cartilage (AC) has limited capacity for repair. The first attempt to repair cartilage using tissue engineering was reported in 1977. Since then, cell-based interventions have entered clinical practice in orthopaedics, and several tissue engineering approaches to repair cartilage are in the translational pipeline towards clinical application. Classically, these involve a scaffold, substrate or matrix to provide structure, and cells such as chondrocytes or mesenchymal stromal cells to generate the tissue. We discuss the advantages and drawbacks of the use of various cell types, natural and synthetic scaffolds, multiphasic or gradient-based scaffolds, and self-organizing or self-assembling scaffold-free systems, for the engineering of cartilage constructs. Several challenges persist including achieving zonal tissue organization and integration with the surrounding tissue upon implantation. Approaches to improve cartilage thickness, organization and mechanical properties include mechanical stimulation, culture under hypoxic conditions, and stimulation with growth factors or other macromolecules. In addition, advanced technologies such as bioreactors, biosensors and 3D bioprinting are actively being explored. Understanding the underlying mechanisms of action of cell therapy and tissue engineering approaches will help improve and refine therapy development. Finally, we discuss recent studies of the intrinsic cellular and molecular mechanisms of cartilage repair that have identified novel signals and targets and are inspiring the development of molecular therapies to enhance the recruitment and cartilage reparative activity of joint-resident stem and progenitor cells. A one-fits-all solution is unrealistic, and identifying patients who will respond to a specific targeted treatment will be critical.

Putative critical quality attribute matrix identifies mesenchymal stromal cells with potent immunomodulatory and angiogenic "fitness" ranges in response to culture process parameters

Adipose-derived mesenchymal stromal cells (MSC(AT)) display immunomodulatory and angiogenic properties, but an improved understanding of quantitative critical quality attributes (CQAs) that inform basal MSC(AT) fitness ranges for immunomodulatory and/or angiogenic applications is urgently needed for effective clinical translation. We constructed an in vitro matrix of multivariate readouts to identify putative CQAs that were sensitive enough to discriminate between specific critical processing parameters (CPPs) chosen for their ability to enhance MSC immunomodulatory and angiogenic potencies, with consideration for donor heterogeneity. We compared 3D aggregate culture conditions (3D normoxic, 3D-N) and 2D hypoxic (2D-H) culture as non-genetic CPP conditions that augment immunomodulatory and angiogenic fitness of MSC(AT). We measured multivariate panels of curated genes, soluble factors, and morphometric features for MSC(AT) cultured under varying CPP and licensing conditions, and we benchmarked these against two functional and therapeutically relevant anchor assays - in vitro monocyte/macrophage (MΦ) polarization and in vitro angiogenesis. Our results showed that varying CPP conditions was the primary driver of MSC(AT) immunomodulatory fitness; 3D-N conditions induced greater MSC(AT)-mediated MΦ polarization toward inflammation-resolving subtypes. In contrast, donor heterogeneity was the primary driver of MSC(AT) angiogenic fitness. Our analysis further revealed panels of putative CQAs with minimum and maximum values that consisted of twenty MSC(AT) characteristics that informed immunomodulatory fitness ranges, and ten MSC(AT) characteristics that informed angiogenic fitness ranges. Interestingly, many of the putative CQAs consisted of angiogenic genes or soluble factors that were inversely correlated with immunomodulatory functions (THBS1, CCN2, EDN1, PDGFA, VEGFA, EDIL3, ANGPT1, and ANG genes), and positively correlated to angiogenic functions (VEGF protein), respectively. We applied desirability analysis to empirically rank the putative CQAs for MSC(AT) under varying CPP conditions and donors to numerically identify the desirable CPP conditions or donors with maximal MSC(AT) immunomodulatory and/or angiogenic fitness. Taken together, our approach enabled combinatorial analysis of the matrix of multivariate readouts to provide putative quantitative CQAs that were sensitive to variations in select CPPs that enhance MSC immunomodulatory/angiogenic potency, and donor heterogeneity. These putative CQAs may be used to prospectively screen potent MSC(AT) donors or cell culture conditions to optimize for desired basal MSC(AT) immunomodulatory or angiogenic fitness.

Intra-articular injection of placental mesenchymal stromal cells ameliorates pain and cartilage anabolism/catabolism in knee osteoarthritis

Background: Knee Osteoarthritis (kOA), the most common joint degenerative disorder, lacks effective therapeutics. Placenta-derived mesenchymal stromal cells (PMSCs) are effective in tissue repairing and generation, which have potential in treating kOA. This study aimed to determine the anti-kOA efficacy of PMSCs and to explore its action mode. Methods: Flow cytometry and three-line differentiation were performed for identification of PMSCs. In vivo, a rat kOA model established by anterior cruciate ligament transection (ACLT) surgery was used to evaluate the efficacy of PMSCs. Histopathological HE and SO staining with Osteoarthritis Research Society International scoring were conducted, and cartilage expressions of MMP13 and Col2 were measured by immunohistochemistry. Pain behavior parameters by mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL), were measured. In vitro, wound healing and cell immunofluorescence assays were conducted to detect the proliferation and migration ability of chondrocytes treated with PMSCs conditioned medium (PMSCs-CM). Quantitative real-time PCR (qRT-PCR) and Western blot (WB) assays were applied to explore the molecular action of PMSCs on chondrocytes. Results: The results of flow cytometry indicated that the surface markers of PMSCs (CD73 > 95%, CD90 > 95%, and CD34 < 2%) were consistent with the typical mesenchymal stromal cells. The in vivo data showed that PMSCs significantly reversed the kOA progression by protection of cartilage, regulation of anabolic (Col2) and catabolic (MMP13) expressions, and relief of pain symptoms. The in vitro data showed that PMSCs promoted chondrocyte proliferation and migration and significantly restored the IL-1β-induced abnormal gene expressions of Col2, Mmp13, Adamts4, Adamts5 and Sox9 and also restored the abnormal protein expressions of Col2, Mmp13 and Sox9 of chondrocytes. The molecular actions of PMSCs on chondrocytes in nested co-culture way or in conditioned medium way were similar, confirming a paracrine-based mode of action. Conclusion: This study demonstrated PMSCs' anti-kOA efficacy and its paracrine-based action mode, providing novel knowledge of PMSCs and suggesting it as a promising cell therapy for treatment of kOA.

Breakthrough of extracellular vesicles in pathogenesis, diagnosis and treatment of osteoarthritis

Osteoarthritis (OA) is a highly prevalent whole-joint disease that causes disability and pain and affects a patient's quality of life. However, currently, there is a lack of effective early diagnosis and treatment. Although stem cells can promote cartilage repair and treat OA, problems such as immune rejection and tumorigenicity persist. Extracellular vesicles (EVs) can transmit genetic information from donor cells and mediate intercellular communication, which is considered a functional paracrine factor of stem cells. Increasing evidences suggest that EVs may play an essential and complex role in the pathogenesis, diagnosis, and treatment of OA. Here, we introduced the role of EVs in OA progression by influencing inflammation, metabolism, and aging. Next, we discussed EVs from the blood, synovial fluid, and joint-related cells for diagnosis. Moreover, we outlined the potential of modified and unmodified EVs and their combination with biomaterials for OA therapy. Finally, we discuss the deficiencies and put forward the prospects and challenges related to the application of EVs in the field of OA.

Human synovial mesenchymal stem cells show time-dependent morphological changes and increased adhesion to degenerated porcine cartilage

The possibility that mesenchymal stem cells (MSCs) can adhere to partial defects or degenerative areas in cartilage remains to be established. The purposes of the present study were to verify the adhesion of synovial MSCs to degenerated cartilage, the time course of that adhesion, and the morphological changes that MSCs might undergo during the adhesion process. The surface of pig cartilage was abraded, and a human synovial MSC suspension was placed on the abraded surface. The proportion/number of MSCs that adhered to the cartilage was quantified by counting non-adhered MSCs, measuring the fluorescence intensity of DiI-labeled MSCs, and scanning electron microscopy (SEM) observations. The presence of microspikes or pseudopodia on the MSCs that adhered to the cartilage was also evaluated. SEM confirmed the adhesion of synovial MSCs to degenerated cartilage. The three independent quantification methods confirmed increases in the proportion/number of adhered MSCs within 10 s of placement and over time up to 24 h. The MSCs that adhered at 10 s had a high proportion of microspikes, whereas those that adhered after 1 h had that of pseudopodia. MSCs showed time-dependent morphological changes and increased adhesion to degenerated cartilage after placement of the human synovial MSC suspension.

The role of extracellular vesicles in osteoarthritis treatment via microenvironment regulation

Osteoarthritis (OA) is a degenerative joint disease that is common among the middle-aged and older populations, causes patients to experience recurrent pain in their joints and negatively affects their quality of life. Currently, therapeutic options for patients with OA consist of medications to alleviate pain and treat the symptoms; however, due to typically poor outcomes, patients with advanced OA are unlikely to avoid joint replacement. In recent years, several studies have linked disrupted homeostasis of the joint cavity microenvironment to the development of OA. Recently, extracellular vesicles (EVs) have received increasing attention in the field of OA. EVs are natural nano-microcarrier materials with unique biological activity that are produced by cells through paracrine action. They are composed of lipid bilayers that contain physiologically active molecules, such as nucleic acids and proteins. Moreover, EVs may participate in local and distal intercellular and intracellular communication. EVs have also recently been shown to influence OA development by regulating biochemical factors in the OA microenvironmental. In this article, we first describe the microenvironment of OA. Then, we provide an overview of EVs, summarize the main types used for the treatment of OA, and describe their mechanisms. Next, we review clinical studies using EVs for OA treatment. Finally, the specific mechanism underlying the application of miRNA-enriched EVs in OA therapy is described.

Gene therapy approaches for equine osteoarthritis

With an intrinsically low ability for self-repair, articular cartilage injuries often progress to cartilage loss and joint degeneration resulting in osteoarthritis (OA). Osteoarthritis and the associated articular cartilage changes can be debilitating, resulting in lameness and functional disability both in human and equine patients. While articular cartilage damage plays a central role in the pathogenesis of OA, the contribution of other joint tissues to the pathogenesis of OA has increasingly been recognized thus prompting a whole organ approach for therapeutic strategies. Gene therapy methods have generated significant interest in OA therapy in recent years. These utilize viral or non-viral vectors to deliver therapeutic molecules directly into the joint space with the goal of reprogramming the cells' machinery to secrete high levels of the target protein at the site of injection. Several viral vector-based approaches have demonstrated successful gene transfer with persistent therapeutic levels of transgene expression in the equine joint. As an experimental model, horses represent the pathology of human OA more accurately compared to other animal models. The anatomical and biomechanical similarities between equine and human joints also allow for the use of similar imaging and diagnostic methods as used in humans. In addition, horses experience naturally occurring OA and undergo similar therapies as human patients and, therefore, are a clinically relevant patient population. Thus, further studies utilizing this equine model would not only help advance the field of human OA therapy but also benefit the clinical equine patients with naturally occurring joint disease. In this review, we discuss the advancements in gene therapeutic approaches for the treatment of OA with the horse as a relevant patient population as well as an effective and commonly utilized species as a translational model.

Injectable Peptide Hydrogel Encapsulation of Mesenchymal Stem Cells Improved Viability, Stemness, Anti-Inflammatory Effects, and Early Stage Wound Healing

Human-adipose-derived mesenchymal stem cells (hADMSCs) are adult stem cells and are relatively easy to access compared to other sources of mesenchymal stem cells (MSCs). They have shown immunomodulation properties as well as effects in improving tissue regeneration. To better stimulate and preserve the therapeutic properties of hADMSCs, biomaterials for cell delivery have been studied extensively. To date, hyaluronic acid (HA)-based materials have been most widely adopted by researchers around the world. PGmatrix is a new peptide-based hydrogel that has shown superior functional properties in 3D cell cultures. Here, we reported the in vitro and in vivo functional effects of PGmatrix on hADMSCs in comparison with HA and HA-based Hystem hydrogels. Our results showed that PGmatrix was far superior in maintaining hADMSC viability during prolonged incubation and stimulated expression of SSEA4 (stage-specific embryonic antigen-4) in hADMSCs. hADMSCs encapsulated in PGmatrix secreted more immune-responsive proteins than those in HA or Hystem, though similar VEGF-A and TGFβ1 release levels were observed in all three hydrogels. In vivo studies revealed that hADMSCs encapsulated with PGmatrix showed improved skin wound healing in diabetic-induced mice at an early stage, suggesting possible anti-inflammatory effects, though similar re-epithelialization and collagen density were observed among PGmatrix and HA or Hystem hydrogels by day 21.

MiR-145-5p restrains chondrogenic differentiation of synovium-derived mesenchymal stem cells by suppressing TLR4

Osteoarthritis (OA) is a progressive degeneration of articular cartilage with involvement of synovial membrane, and subchondral bone. Recently, cell-based therapies, including the application of stem cells such as mesenchymal stem cells (MSCs), have been introduced for restoration of the articular cartilage. Toll-like receptors (TLRs) were reported to participate in OA progression and MSC chondrogenesis. Here, the role and molecular mechanism of toll like receptor 4 (TLR4) in chondrogenic differentiation of synovium-derived MSCs (SMSCs) were investigated. Molecular markers (CD44, CD90, CD45 and CD14) on SMSC surfaces were identified by flow cytometry. Multi-potential differentiation capacities of SMSCs for chondrogenesis, adipogenesis and osteogenesis were examined by Alcian blue, oil red O and Alizarin red staining, respectively. TLR4 and miR-145-5p levels in SMSCs were assessed using RT-qPCR. The protein expression of TGFB3, Col II, SOX9 and Aggrecan in SMSCs was tested by western blotting. Cytokine secretions were analyzed with ELISA for IL-1β and IL-6. Intracellular NAD⁺ content and NAD⁺/NADH ratio were assessed. The interaction between miR-145-5p and TLR4 was confirmed by RNA pulldown and luciferase reporter assays. In this study, SMSCs were identified to have immunophenotypic characteristics of MSCs. TLR4 knockdown inhibited chondrogenic and osteogenic differentiation of SMSCs. Mechanistically, TLR4 was targeted by miR-145-5p in SMSCs. Moreover, TLR4 elevation offset the inhibitory impact of miR-145-5p upregulation on chondrogenic differentiation of SMSCs. Overall, miR-145-5p restrains chondrogenesis of SMSCs by suppressing TLR4.

Clearance of senescent cells with ABT-263 improves biological functions of synovial mesenchymal stem cells from osteoarthritis patients

BACKGROUND

Osteoarthritis (OA) is an age-related joint disease characterized by progressive cartilage loss. Synovial mesenchymal stem cells (MSCs) are anticipated as a cell source for OA treatment; however, synovial MSC preparations isolated from OA patients contain many senescent cells that inhibit cartilage regeneration through their senescence-associated secretory phenotype (SASP) and poor chondrogenic capacity. The aim of this study was to improve the biological function of OA synovial MSCs by removing senescent cells using the senolytic drug ABT-263.

METHODS

We pretreated synovial MSCs derived from 5 OA patients with ABT-263 for 24 h and then evaluated senescence-associated beta-galactosidase (SA-β-gal) activity, B cell lymphoma 2 (BCL-2) activity, apoptosis, surface antigen expression, colony formation ability, and multipotency.

RESULTS

The ABT-263 pretreatment significantly decreased the percentage of SA-β-gal-positive cells and BCL-2 expression and induced early- and late-stage apoptosis. Cleaved caspase-3 was expressed in SA-β-gal-positive cells. The pretreated MSCs formed greater numbers of colonies with larger diameters. The expression rate of CD34 was decreased in the pretreated cells. Differentiation assays revealed that ABT-263 pretreatment enhanced the adipogenic and chondrogenic capabilities of OA synovial MSCs. In chondrogenesis, the pretreated cells produced greater amounts of glycosaminoglycan and type II collagen and showed lower expression of senescence markers (p16 and p21) and SASP factors (MMP-13 and IL-6) and smaller amounts of type I collagen.

CONCLUSION

Pretreatment of synovial MSCs from OA patients with ABT-263 can improve the function of the cells by selectively eliminating senescent cells. These findings indicate that ABT-263 could hold promise for the development of effective cell-based OA therapy.

Orthobiologics for the Management of Early Arthritis in the Middle-Aged Athlete

This article is dedicated to the use of orthobiologic therapies in the management of early osteoarthritis in middle-aged athletes. Understanding a patient's presenting symptoms, physical examination, imaging results, and goals is of critical importance in applying orthobiologic therapies. The field of orthobiologics is expanding at a rapid pace, and the clinical studies examining the utility of each treatment lag behind the direct-to-consumer marketing that leads to these products being used. Here we provide a review of the available treatments, emerging treatments, and the current literature supporting or refuting their use. Currently studied orthobiologics include autologous and allogenic cell therapies, autologous blood products, hyaluronic acid, gene therapies, Wnt inhibitors, and a variety of systemic treatments.

Human induced mesenchymal stem cells display increased sensitivity to matrix stiffness

The clinical translation of mesenchymal stem cells (MSCs) is limited by population heterogeneity and inconsistent responses to engineered signals. Specifically, the extent in which MSCs respond to mechanical cues varies significantly across MSC lines. Although induced pluripotent stem cells (iPSCs) have recently emerged as a novel cell source for creating highly homogeneous MSC (iMSC) lines, cellular mechanosensing of iMSCs on engineered materials with defined mechanics is not well understood. Here, we tested the mechanosensing properties of three human iMSC lines derived from iPSCs generated using a fully automated platform. Stiffness-driven changes in morphology were comparable between MSCs and iMSCs cultured atop hydrogels of different stiffness. However, contrary to tissue derived MSCs, no significant changes in iMSC morphology were observed between iMSC lines atop different stiffness hydrogels, demonstrating a consistent response to mechanical signals. Further, stiffness-driven changes in mechanosensitive biomarkers were more pronounced in iMSCs than MSCs, which shows that iMSCs are more adaptive and responsive to mechanical cues than MSCs. This study reports that iMSCs are a promising stem cell source for basic and applied research due to their homogeneity and high sensitivity to engineered mechanical signals.

Mesenchymal stem cell treatment for enteric neuropathy in the Winnie mouse model of spontaneous chronic colitis

Inflammatory bowel disease (IBD) is a chronic gut inflammation with periods of acute flares and remission. Beneficial effects of a single dose of mesenchymal stem cell (MSC)-based treatment have been demonstrated in acute models of colitis. No studies investigated therapeutic effects of MSCs for the attenuation of enteric neuropathy in a chronic model of colitis. The short and long-term effects of MSC treatment in modulating inflammation and damage to the enteric nervous system (ENS) were studied in the Winnie mouse model of spontaneous chronic colitis highly representative of human IBD. Winnie mice received a single dose of either 1 × 10⁶ human bone marrow-derived MSCs or 100µL PBS by intracolonic enema. C57BL/6 mice received 100µL PBS. Colon tissues were collected at 3 and 60 days post MSC administration to evaluate the short-term and long-term effects of MSCs on inflammation and enteric neuropathy by histological and immunohistochemical analyses. In a separate set of experiments, multiple treatments with 4 × 10⁶ and 2 × 10⁶ MSCs were performed and tissue collected at 3 days post treatment. Chronic intestinal inflammation in Winnie mice was associated with persistent diarrhea, perianal bleeding, morphological changes, and immune cell infiltration in the colon. Significant changes to the ENS, including impairment of cholinergic, noradrenergic and sensory innervation, and myenteric neuronal loss were prominent in Winnie mice. Treatment with a single dose of bone marrow-derived MSCs was ineffective in attenuating chronic inflammation and enteric neuropathy in Winnie.

Mesenchymal Stem Cells Derived from Umbilical Cord Blood having Excellent Stemness Properties with Therapeutic Benefits - a New Era in Cancer Treatment

Mesenchymal stem cells (MSCs) are the most promising candidates for cellular therapies, and most therapeutic applications have focused on MSCs produced from adult bone marrow, despite mounting evidence that MSCs are present in a wide range of conditions. Umbilical cord blood (UCB) is a valuable source of hematopoietic stem cells, but its therapeutic potential extends beyond the hematopoietic component, which also suggests solid organ regenerative potential. With potential ranging from embryonic-like to lineage-committed progenitor cells, many different stems and progenitor cell populations have been postulated. MSC is currently inferred by numerous clinical applications for human UCB. aAs stem cell therapy kicks off some new research and these cells show such a boon to stem cell therapy, it is nevertheless characteristic that the prospect of UCB conservation is gaining momentum. Taken together, the experience described here shows that MSCs derived from UCB are seen as attractive therapeutic candidates for various human disorders including cancer. It is argued that a therapeutic stem cell transplant, using stem cells from UCB, provides a reliable repository of early precursor cells that can be useful in a large number of different conditions, considering issues of safety, availability, transplant methodology, rejection, and side effects. In particular, we focus on the concept of isolation and expansion, comparing the phenotype with MSC derived from the UCB, describing the ability to differentiate, and lastly, the therapeutic potential concerning stromal support, stemness characteristic, immune modulation, and cancer stem cell therapy. Thus it is an overview of the therapeutic application of UCB derived MSCs, with a special emphasis on cancer. Besides, the current evidence on the double-edged sword of MSCs in cancer treatment and the latest advances in UCB-derived MSC in cancer research will be discussed.

Yields of mesenchymal stromal cells from synovial fluid reflect those from synovium in patients with rheumatoid arthritis

The yield of primary synovial mesenchymal stromal cells (MSCs) from synovium of patients with rheumatoid arthritis (RA) is highly variable, but cell transplantation therapy with autologous synovial MSCs requires accurate prediction of the synovial MSC yield per synovium weight. Here, we determined whether the yield of synovial fluid MSCs might predict the ultimate yield of primary MSCs from the synovium of RA knees. Synovial fluid and synovium were harvested during total knee arthroplasty from the knee joints of 10 patients with RA. Synovial fluid (1.5 mL) was diluted fourfold and plated equally into six 60 cm² dishes. Nucleated cells from digested synovium were similarly plated at 1 × 10⁴ cells in 6 dishes. All dishes were cultured for 14 days and analyzed for MSC yields and properties, including in vitro chondrogenesis. The cultured synovial cell number was correlated with the cultured synovial fluid cell number (n = 10, R² = 0.64, p < 0.01). Synovial fluid cells formed cell colonies and showed MSC-like surface epitopes and multi-differentiation potential. However, the cartilage pellet weight indicated a greater chondrogenic potential of the synovial MSCs (n = 8). The primary MSC yields from synovial fluid and synovium were correlated, indicating that the synovial fluid MSC yield can predict the ultimate synovial MSC yield.

NSAIDs Reduce Therapeutic Efficacy of Mesenchymal Stromal Cell Therapy in a Rodent Model of Posttraumatic Osteoarthritis

BACKGROUND

Intra-articular injections of human mesenchymal stromal cells (hMSCs) have shown promise in slowing cartilage degradation in posttraumatic osteoarthritis (PTOA). Clinical use of cell therapies for osteoarthritis has accelerated in recent years without sufficient scientific evidence defining best-use practices. Common recommendations advise patients to avoid nonsteroidal anti-inflammatory drug (NSAID) use before and after cell injection over concerns that NSAIDs may affect therapeutic efficacy. Recommendations to restrict NSAID use are challenging for patients, and it is unclear if patients are compliant.

HYPOTHESIS

NSAIDs will reduce the efficacy of hMSC therapy in treating a preclinical model of PTOA.

STUDY DESIGN

Controlled laboratory study.

METHODS

Lewis rats underwent medial meniscal transection (MMT) surgery to induce PTOA or a sham (sham group) surgery that did not progress to PTOA. Rats received naproxen solution orally daily before (Pre-NSAID group) or after (Post-NSAID group) hMSC treatment, throughout the course of the experiment (Full-NSAID group), or received hMSCs without NSAIDs (No NSAID). Cartilage morphology and composition were quantified using contrast-enhanced micro-computed tomography and histology. Pain (secondary allodynia) was measured using a von Frey filament.

RESULTS

Injection of hMSCs attenuated cartilage degeneration associated with MMT. hMSCs prevented proteoglycan loss, maintained smooth cartilage surfaces, reduced cartilage lesions, reduced mineralized osteophyte formation, and reduced pain by week 7. The Pre-NSAID group had decreased proteoglycan levels compared with the hMSC group, although there were no other significant differences. Thus, pretreatment with NSAIDs had minimal effects on the therapeutic benefits of hMSC injections. The Post-NSAID and Full-NSAID groups, however, exhibited significantly worse osteoarthritis than the hMSC-only group, with greater proteoglycan loss, surface roughness, osteophyte volume, and pain.

CONCLUSION

Use of NSAIDs before hMSC injection minimally reduced the therapeutic benefits for PTOA, which included preservation of cartilage surface integrity as well as a reduction in osteophytes. Use of NSAIDs after injections, however, substantially reduced the therapeutic efficacy of cellular treatment.

CLINICAL RELEVANCE

Our data support the clinical recommendation of avoiding NSAID use after hMSC injection but suggest that using NSAIDs before treatment may not substantially diminish the therapeutic efficacy of cell treatment.

Preclinical studies and clinical trials on mesenchymal stem cell therapy for knee osteoarthritis: A systematic review on models and cell doses

AIM

To provide a systematic analysis of the study design in knee osteoarthritis (OA) preclinical studies, focusing on the characteristics of animal models and cell doses, and to compare these to the characteristics of clinical trials using mesenchymal stem cells (MSCs) for the treatment of knee OA.

METHOD

A systematic and comprehensive search was conducted using the PubMed, Web of Science, Ovid, and Embase electronic databases for research papers published in 2009-2020 on testing MSC treatment in OA animal models. The PubMed database and ClinicalTrials.gov website were used to search for published studies reporting clinical trials of MSC therapy for knee OA.

RESULTS

In total, 9234 articles and two additional records were retrieved, of which 120 studies comprising preclinical and clinical studies were included for analysis. Among the preclinical studies, rats were the most commonly used species for modeling knee OA, and anterior cruciate ligament transection was the most commonly used method for inducing OA. There was a correlation between the cell dose and body weight of the animal. In clinical trials, there was large variation in the dose of MSCs used to treat knee OA, ranging from 1 × 10⁶ to 200 × 10⁶ cells with an average of 37.91 × 10⁶ cells.

CONCLUSION

Mesenchymal stem cells have shown great potential in improving pain relief and tissue protection in both preclinical and clinical studies of knee OA. Further high-quality preclinical and clinical studies are needed to explore the dose effectiveness relationship of MSC therapy and to translate the findings from preclinical studies to humans.

Injectable amnion hydrogel-mediated delivery of adipose-derived stem cells for osteoarthritis treatment

Current treatment strategies for osteoarthritis (OA) predominantly address symptoms with limited disease-modifying potential. There is a growing interest in the use of adipose-derived stem cells (ADSCs) for OA treatment and developing biomimetic injectable hydrogels as cell delivery systems. Biomimetic injectable hydrogels can simulate the native tissue microenvironment by providing appropriate biological and chemical cues for tissue regeneration. A biomimetic injectable hydrogel using amnion membrane (AM) was developed which can self-assemble in situ and retain the stem cells at the target site. In the present study, we evaluated the efficacy of intraarticular injections of AM hydrogels with and without ADSCs in reducing inflammation and cartilage degeneration in a collagenase-induced OA rat model. A week after the induction of OA, rats were treated with control (phosphate-buffered saline), ADSCs, AM gel, and AM-ADSCs. Inflammation and cartilage regeneration was evaluated by joint swelling, analysis of serum by cytokine profiling and Raman spectroscopy, gross appearance, and histology. Both AM and ADSC possess antiinflammatory and chondroprotective properties to target the sites of inflammation in an osteoarthritic joint, thereby reducing the inflammation-mediated damage to the articular cartilage. The present study demonstrated the potential of AM hydrogel to foster cartilage tissue regeneration, a comparable regenerative effect of AM hydrogel and ADSCs, and the synergistic antiinflammatory and chondroprotective effects of AM and ADSC to regenerate cartilage tissue in a rat OA model.

Synovial membrane mesenchymal stem cells for cartilaginous tissues repair

BACKGROUND

The present review is focused on general aspects of the synovial membrane as well as specialized aspects of its cellular constituents, particularly the composition and location of synovial membrane mesenchymal stem cells (S-MSCs). S-MSC multipotency properties are currently at the center of translational medicine for the repair of multiple joint tissues, such as articular cartilage and meniscus lesions.

METHODS AND RESULTS

We reviewed the results of in vitro and in vivo research on the current clinical applications of S-MSCs, surface markers, cell culture techniques, regenerative properties, and immunomodulatory mechanisms of S-MSCs as well as the practical limitations of the last twenty-five years (1996 to 2021).

CONCLUSIONS

Despite the poor interest in the development of new clinical trials for the application of S-MSCs in joint tissue repair, we found evidence to support the clinical use of S-MSCs for cartilage repair. S-MSCs can be considered a valuable therapy for the treatment of repairing joint lesions.

Synovium Derived Mesenchymal Stromal Cells (Sy-MSCs): A Promising Therapeutic Paradigm in the Management of Knee Osteoarthritis

Synovium-derived mesenchymal stromal cell (Sy-MSC) is a newer member of the mesenchymal stromal cell families. The first successful demonstration of the mesenchymal stromal cell from the human synovial membrane was done in 2001 and since then its potential role for musculoskeletal regeneration has been keenly documented. The regenerative effects of Sy-MSCs are through paracrine signaling, direct cell-cell interactions, and extracellular vehicles. Sy-MSCs possess superior chondrogenicity than other sources of mesenchymal stromal cells. This article aims to outline the advancement of synovium-derived mesenchymal stromal cells along with a specific insight into the application for managing osteoarthritis knee.

A low dose cell therapy system for treating osteoarthritis: In vivo study and in vitro mechanistic investigations

Mesenchymal stem cells (MSCs) can be effective in alleviating the progression of osteoarthritis (OA). However, low MSC retention and survival at the injection site frequently require high doses of cells and/or repeated injections, which are not economically viable and create additional risks of complications. In this study, we produced MSC-laden microcarriers in spinner flask culture as cell delivery vehicles. These microcarriers containing a low initial dose of MSCs administered through a single injection in a rat anterior cruciate ligament (ACL) transection model of OA achieved similar reparative effects as repeated high doses of MSCs, as evaluated through imaging and histological analyses. Mechanistic investigations were conducted using a co-culture model involving human primary chondrocytes grown in monolayer, together with MSCs grown either within 3D constructs or as a monolayer. Co-culture supernatants subjected to secretome analysis showed significant decrease of inflammatory factors in the 3D group. RNA-seq of co-cultured MSCs and chondrocytes using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed processes relating to early chondrogenesis and increased extracellular matrix interactions in MSCs of the 3D group, as well as phenotypic maintenance in the co-cultured chondrocytes. The cell delivery platform we investigated may be effective in reducing the cell dose and injection frequency required for therapeutic applications.

Synovial mesenchymal stem cell-derived exosomal miR-320c enhances chondrogenesis by targeting ADAM19

Background: Synovial mesenchymal stem cell (SMSC)-derived exosomes show treatment potential in osteoarthritis, although their functional mechanism is still unclear. Materials & methods: Osteoarthritis chondrocytes and normal SMSC were cultured. Subsequently, chondrocytes were co-cultured with SMSC or miR-320c-overexpressing SMSC-derived exosomes, or directly transfected with miR-320c mimic. Furthermore, compensate experiments were conducted. Results: SMSC promoted chondrocyte proliferation, migration, COL2A1 and ACAN expressions while suppressing apoptosis by transmitting exosomes. Furthermore, miR-320c-overexpressing SMSC-derived exosomes and direct miR-320c overexpression in chondrocytes presented more significant effect on enhancing chondrogenesis. In addition, miR-320c directly targeted ADAM19, and ADAM19 overexpression compensated the regulation of miR-320c on chondrogenesis. Conclusion: SMSC-derived exosomal miR-320c enhances chondrogenesis through targeting ADAM19, highlighting a potentially novel mechanism of SMSC in treating osteoarthritis.

Cell and Cell Free Therapies in Osteoarthritis

Osteoarthritis (OA) is the most common articular disease in adults and has a current prevalence of 12% in the population over 65 years old. This chronic disease causes damage to articular cartilage and synovial joints, causing pain and leading to a negative impact on patients' function, decreasing quality of life. There are many limitations regarding OA conventional therapies-pharmacological therapy can cause gastrointestinal, renal, and cardiac adverse effects, and some of them could even be a threat to life. On the other hand, surgical options, such as microfracture, have been used for the last 20 years, but hyaline cartilage has a limited regeneration capacity. In recent years, the interest in new therapies, such as cell-based and cell-free therapies, has been considerably increasing. The purpose of this review is to describe and compare bioregenerative therapies' efficacy for OA, with particular emphasis on the use of mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP). In OA, these therapies might be an alternative and less invasive treatment than surgery, and a more effective option than conventional therapies.

Synovial Fluid Mesenchymal Stem Cells for Knee Arthritis and Cartilage Defects: A Review of the Literature

Mesenchymal stem cells (MSCs) are adult stem cells that have the ability to self-renew and differentiate into several cell lineages including adipocytes, chondrocytes, tenocytes, bones, and myoblasts. These properties make the cell a promising candidate for regenerative medicine applications, especially when dealing with sports injuries in the knee. MSCs can be isolated from almost every type of adult tissue. However, most of the current research focuses on MSCs derived from bone marrow, adipose, and placenta derived products. Synovial fluid-derived MSCs (SF-MSCs) are relatively overlooked but have demonstrated promising therapeutic properties including possessing higher chondrogenic proliferation capabilities than other types of MSCs. Interestingly, SF-MSC population has shown to increase exponentially in patients with joint injury or disease, pointing to a potential use as a biomarker or as a treatment of some orthopaedic disorders. In this review, we go over the current literature on synovial fluid-derived MSCs including the characterization, the animal studies, and discuss future perspectives.